Biology Lectures 4-6 Flashcards
What are Lipids?
Lipids are LARGE biological molecules which are formed of C, H, O and sometimes P.
What are Lipids NOT?
Polymers
Properties of lipids? Why do they have these properties?
Lipids are largely NON-POLAR because mostly made up of C-H and C-C bonds.
Lipids are INSOULBLE in water because the is no slightly positive/ negative end for the water to attract to. Lipids can be SOLUBLE in NON- POLAR solvents.
HYDROPHOBIC interactions cause lipids to group together in water.
Give some examples of lipids.
FATS- solid at room temperature. OILS- liquids at room temperature. WAXES- solid at room temperature- very hydrophobic. PHOSPHOLIPIDS forms membrane bilayer. STEROIDS
What are Triglycerides?
Type of dietary fat.
What are Triglycerides formed of?
Formed of 1 GYCEROL (backbone) and 3 FATTY ACID chains.
What bond is present between a fatty acid chain and glycerol?
ESTER BOND.
How are Triglycerides formed?
DEHYDRATION synthesis (condensation reactions).
How are Triglycerides broken down? What enzyme does this require?
HYDROYLSIS reactions which requires the intestinal enzyme TRIGLYCERIDE LIPASE.
Why are Triglycerides broken down?
Free fatty acids are more easily absorbed in the gut and transported.
Name the two types of classes of Triglycerides.
Saturated and Unsaturated.
What are Saturated fatty acids? Give an example of a saturated fatty acid.
SATURATED fatty acids contain SINGLE carbon- carbon bonds. Examples include PALMITATE.
What type of triglyceride does saturated fatty acids form. Give an example of one.
SFAs (Saturated Fatty Acids) form COMPACT, closely packed triglycerides that are solid at room temperature, for example Palmitic acid present in plant and animal fats.
What are unsaturated fatty acids. Give an example of a unsaturated fatty acid.
UNSATURATED fatty acids contain 1 or more carbon- carbon DOUBLE bonds. Examples include OLEATE.
What type of triglyceride does unsaturated fatty acids form. Why? Give an example of one.
UTAs (Unsaturated Fatty Acids) form LOOSELY packed triglycerides due to the double bonds and is a liquid at room temperature, for example Olive Oil.
What are free fatty acids?
Are when the fatty acid is not part of a triglyceride.
Why are free fatty acids essential?
NOT synthesised by the body.
How do you name an “omega FFAs”?
find the location of the first double bond counting from the methyl end.
What is the basic structure of steroids?
FOUR FUSED CARBON RINGS with various side groups.
What is the building block of steroids?
How is the building block formed?
LANOSTEROL is the building block of all steroids and is formed by the cyclization of SQUALENE (long chain).
Name some examples of Steroids.
Cholesterol, sex hormones like Oestrogen, Corticosteroids produced in the adrenal cortex and with many functions include controlling inflammation as well as Vitamin D.
What are phospholipids?
PHOSPHOLIPIDS are lipids with a PHOSPHATE GROUP COVALENTLY bonded to the glycerol backbone instead of a fatty acid.
Properties of a phosphate group and a fatty acid group.
PHOSPHATE GROUP Polar Soluble in water (hydrophilic) head FATTY ACID GROUPS Non-polar Insoluble in water (hydrophobic) Tail
What ways can phospholipids be arranged in water? Why?
MICELLE which is a spherical arrangement of lipid molecules or a BILAYER which is composed of two layers of lipids organised as a sheet.
Phospholipids like to keep their “HEADS WET” and their “TAILS DRY.”
What are glycolipids?
GLYCOLIPIDS are lipids which are COVALENTLY attached to an OLIGOSACCHARIDE (3-20 monomers).
What do glycolipids form part of?
Form part of the cell membrane and glycocalyx, carbohydrate enriched coating that covers the outside of eukaryotic and prokaryotic cells in particular bacteria.
What are lipoproteins? Where are they found?
LIPOPROTEINS are soluble complexes that transport lipids and are synthesized in the liver.
What Spherical particles have a central HYDROPHOBIC core?
Triglycerides
Esterified cholesterol (cholesteryl ester)
Small amounts of other lipids and fat soluble vitamins.
What particles have an External HYDROPHILIC layer:
Phospholipids Cholesterol (OH functional group) Apoproteins- Stabilise structure and regulate enzymatic activity at the lipoprotein interface.
Lipoprotein- What fat does Chylomicrons carry? From where to where?
Carry dietary fat from small intestine to liver.
What does VLDL stand for?
Where are VLDL produced and what are they synthesised from?
What fat does it carry?
How does VLDL become IDL and then LDL?
Very Low Density Lipoprotein.
Produced in Liver and synthesised from Triglycerides and Cholesterol Ester.
Gradually TGs are removed to produced Intermediate Density and Low Density Lipoproteins.
What does HDL stand for?
What does HDL do? Why?
What is the condition?
High Density Lipoprotein
HDL carries (good) cholesterol to the liver which reduces atherosclerosis.
Atherosclerosis is a serious condition where arteries become clogged with fatty material. Sites of fatty deposition called plaques.
What is the optimal lipoprotein profile?
HDL: >60 mg/dL
LDL: 60- 130 mg/dL
TGs: <150 mg/dL
Total Cholesterol: < 200 mg/dL
How triglycerides stored? Where are they stored?
Lipid droplets in the cytoplasm of ADIPOCYTE cells in ADIPOSE TISSUE.
What does white adipose tissue do?
Cushion internal organs Acts as a shock absorber Gives insulation Reduces Skin Heat loss Protects internal organs from temperature change.
Name an example of where white adipose tissue is found.
Gluteals
What is the main function of brown adipose tissue? What does it have which allows to carry out this function.
BROWN adipose tissue is useful for generating body heat as in the adipocytes cells there are lots of fat vacuoles and mitochondria.
Name a location in the body where brown adipose tissue is found.
Neck
What can excess adipose tissue lead to?
Atherosclerosis
Thrombosis- clotting of circulating blood
Stenosis- abnormal narrowing of blood vessel
Aneurysms- blood- filled bulges in a blood Bessel wall.
Exerts undue pressure on organs and is a major endocrine organ which produces pro-inflammatory hormones such as leptin and the cytokine TNFα.
What insulation do phospholipids provide? What does this insulation do?
MYELIN INSULATION around nerve fibres.
Myelin increases the speed of nerve impulses.
What are the functions of Vitamins A, D, E and K which are fat soluble and some are lipid/ steroid derived.
Vitamin A- Retinol- Health teeth, skin and sight.
Vitamin D- Cholecalciferol- Helps body absorb Ca2+ for health bones.
Vitamin E- Tocopherol found in oils- Anti- Oxidant, protects cells from damage.
Vitamin K- Phylloquinone and Menaquinone- Important for coagulation of blood.
Chemical messengers and are steroidal hormones are derived from what?
Cholesterol
Lipid layers can prevent what, especially in the eye and on the skin?
EVAPOURATION of water.
A Lipid layer on tear film reduces moisture loss from the CORNEA.
What are proteins?
Proteins are POLYMERIC, chain- like molecules which have fundamental cellular components which are vital for all cellular functions.
What is a polypeptide?
A POLYPEPTIDE is amino acid monomers linked together by PEPTIDE BONDS
How many amino acids is a polypeptide made up of?
More than 40 amino acids and can fold to determine shape.
What does the protein sequence determine?
SHAPE and FUNCTION of a protein.
How many amino acids are there?
20 amino acids.
What do all amino acids have? Is there any exceptions?
All amino acids have a CHIRAL CARBON, a CARBOXYL GROUP, an AMINE GROUP. Each Amino acid has a different side chain (R group). Apart from one exception, the Carbon in all amino acids is chiral.
What is a chiral carbon?
A CHIRAL CARBON is an atom in a molecule which is bonded to 4 different chemical species.
Since all amino acids have a chiral carbon they have two what? What are there names? Which occurs more in nature?
Two ENANTOMERS which are NOT SUPERIMPOSABLE MIRROR IMAGES or L and D forms. L form is dominate with the D form rare in nature.
Amino Acid Ionisation- in a low pH environment what happens to concentration of H+ so what amino acid is favourable there?
In a LOW pH environment there is a HIGH concentration of H+ ions so the amino acid gains a H+ ion on the amine group and so has a POSITIVE charge on the amine group.
Amino Acid Ionisation- in a high pH environment what happens to concentration of H+ so what amino acid is favourable there?
In a HIGH pH environment there is a LOW concentration of H+ ions so the amino acid loses a H+ ion from the Carboxyl group and so has a NEGATIVE charge on the carboxyl group.
What is a Zwitterion seen as?
The middle- Has an extra H+ on NH2 and COO-
What determines the properties of an amino acid?
R group.
Classify the amino acids into different R groups.
Hydrophobic:
9 Non polar
Hydrophilic:
6 Polar
2 Acidic
3 Basic
What amino acids have non- polar R groups?
Glycine (gly) Alanine (Ala) Valine (Val) Leucine (Leu) Isoleucine (ile) Methionine (Met) Phenylalanine (Phe) Tryptophan (Trp) Proline (Pro)
Name the amino acids which have acidic R groups? Why do they have acidic R groups?
What is an acid?
Aspartic Acid and Glutamic Acid
In NORMAL conditions Asp and Glu have a lower pKa so are a stronger acid so will LOSE protons off the OH and become O- so are negatively charged.
ACID= PROTON DONER
Name the amino acids which have basic R groups? Why do they have basic R groups?
What is an base?
Lysine (lys)
Arginine (Arg)
Histidine (his)
In NORMAL conditions Lys, Arg and His have a higher pKa so are a weaker acid so will GAIN protons and become NH3 + so is positively charged.
BASE= PROTON ACCEPTOR
Name the amino acids which have polar R groups? What is these groups main property?
Tyrosine (Try) Asparagine (Asn) Glutamine (Gln) Serine (Ser) Threonine (The) Cysteine (Cys)
Can form hydrogen bond interactions with similar side-chains and peptide bonds.
What can the Amino Acid Cys form?
can form disulphide bridges which is a COVALENT link between two Sulphurs on two different polypeptides.
How are polypeptides formed?
What is the name of the reaction?
What bond is formed in this reaction?
Polypeptides are formed by DEHYDRATION SYNTHESIS which is achieved via linkage of -COOH and -NH2.
A WATER molecule is removed in a CONDENSATION REACTION which results in the formation of a PEPTIDE BOND.
Describe a peptide bond. Why does the bond have these properties?
Peptide bonds are RIGID and PLANAR because of the electrons in the bond.
Rotation at C is usually limited by steric clashes between bulky R groups, so the TRANS form is the most common.
What is the primary structure of a protein?
Amino acid sequence.
What is the secondary structure of a protein?
Interactions between adjacent amino acids. Examples include α helices, b- sheets, loops/random coils.
What is the tertiary structure of a protein?
3D folding of a single polypeptide chain.
What is the quaternary structure of a protein?
Assembly of multiple proteins into a complex.
What determines the amino acid sequence?
DNA sequence of GENES for each protein
What will alter the primary sequence of a protein? Give an example.
Genetic mutations which alter the primary structure cause a change to the STRUCTURE and FUNCTION of the protein, for example sickle cell disease.
What do Alpha helices and beta pleated sheets do in the secondary structure?
ALPHA HELICES and BETA PLEATED SHEET are parts of the polypeptide chains that take on regular patterns of hydrogen bonding. The patterns are connected by SHORT TUNRS and longer LOOPS/ RANDOM COILS.
